This one surprised me. I mean, there had been some gossip on HuffPo about the possibility about the time the GOP was bashing Senators Specter, Collins, and Snowe for voting with the administration on the stimulus bill. I would never be surprised by Specter voting with the administration, he has more in common with moderate and conservative Democrats than with reactionary Republicans. Yet I would not have believed he would so willingly give the Democratic caucus a filibuster proof majority.
After all, the election judges have ruled that Al Franken won the Minnesota Senate race and it is unlikely that the state Supreme Court will overturn the election, now that the ballots have been counted. Which means, when Franken is seated, that will make 60 (counting independent Joe Lieberman and Democratic Socialist Bernie Sanders) votes in the Democratic caucus. Though Specter denies that he will be 'an automatic 60th vote for cloture', the pressure he feels in the Democratic caucus will be very different from the kind of pressure he felt in the Republican caucus. Rather than being pushed to obstruct, he will be pushed to help govern.
I have never been a huge Specter fan, but my biggest problem with him has always been the way he beat up Anita Hill during the confirmation hearing of Justice Clarence Thomas. His voting record has shown the kind of attempt to exercise sound and independent judgement that can and should be admired. He has never been either an ideologically rabid conservative nor a knee-jerk liberal. He's been left of most Republicans on abortion and gay rights, though hardly a leader on either issue. I understand that this move is primarily one about political self-protection and that the GOP essentially pushed him into this. I think it a terrible mistake on their part. He does them much more damage as a Democrat than he did them as a moderate Republican, and this only happened because the Republican Party chose to make it happen.
Watch two members of the Democratic caucus, however: Senator Ben Nelson (D - Nebraska) and Joe Lieberman. Either one could decide they have more power in a Senate that is not filibuster proof. Lieberman could jump caucuses and Nelson could drop his Democratic party affiliation and join the Republican caucus as an independent. If either happens, don't be shocked.